Where does “pyrz” come from?

pyrz (Old Polish) comes from Proto-Slavic pyrь, from Proto-Indo-European péh₂wr̥ — bonfire; spelt.

Ancestry of “pyrz”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	pyrь	remains of fire, smoldering ash, cinder; wild...
2	Proto-Indo-European	péh₂wr̥	bonfire; spelt

pyrz — Etymology, Origin & Word History | Etymology Explorer